The Tree of LifeThe Tree of Life

Chapter 17Chapter 17

11

17.1 Taxonomy17.1 Taxonomy

The science of naming The science of naming and classifying organismsand classifying organisms

2000 years ago – 2000 years ago – AristotleAristotle Grouped plants and animalsGrouped plants and animals Based on structural Based on structural

similaritiessimilarities Greeks and Romans Greeks and Romans

included categoriesincluded categories Genus = Latin for groupGenus = Latin for group

22

TaxonomyTaxonomy

Mid – 1700’s Mid – 1700’s Naming organismsNaming organisms

PolynomialsPolynomials Descriptive phrasesDescriptive phrases European honeybeeEuropean honeybee

Apis pubescens, thorace Apis pubescens, thorace subgriseo, abdomine fusco, subgriseo, abdomine fusco, pedibus posticis glabis, pedibus posticis glabis, untrinque margine ciliatusuntrinque margine ciliatus

33

Simpler SystemSimpler System

Carl LinnaeusCarl Linnaeus Swedish biologist Swedish biologist Developed Developed binomial binomial

nomenclaturenomenclature Two-part naming Two-part naming

systemsystem

Ex: European Ex: European honeybeehoneybee Apis melliferaApis mellifera

44

Scientific NamesScientific Names

Unique two-part Unique two-part name for a speciesname for a species

Genus Genus - - First nameFirst name Taxonomic category Taxonomic category

of similar organismsof similar organisms Organisms have Organisms have

common important common important characteristicscharacteristics

55

Scientific NamesScientific Names

Species Species = Second = Second name name One specific kind of One specific kind of

living thingliving thing Identifies the Identifies the

particular type of particular type of organismorganism

Most specific and Most specific and basic naming unit basic naming unit

66

Rules for Scientific Rules for Scientific NamesNames

GenusGenus Always first Always first Capitalized 1Capitalized 1stst letter letter

SpeciesSpecies Always secondAlways second NOT capitalizedNOT capitalized

BothBoth ItalicizedItalicized or or underlinedunderlined Base on Latin languageBase on Latin language

Apis melliferaApis mellifera

77

Scientific NamesScientific Names

Conform to rules Conform to rules establishedestablished

No two the sameNo two the same Gives biologist Gives biologist

common way of common way of communicatingcommunicating

CommonCommon names have names have problemsproblems Ex: RobinEx: Robin

Different bird in US Different bird in US and England!and England!

88

Classifying OrganismsClassifying Organisms

Carl LinnaeusCarl Linnaeus Classification systemClassification system

Ranked system of Ranked system of groupsgroups

Large groups Large groups subdivided into smaller subdivided into smaller groupsgroups

Increasingly similarIncreasingly similar 7 groups total7 groups total

Now we have one Now we have one more groupmore group = Eight group levels= Eight group levels

99

Classifying OrganismsClassifying Organisms

Groups Groups DomainDomain KingdomKingdom PhylumPhylum ClassClass Order Order FamilyFamily GenusGenus SpeciesSpecies

DefinitionDefinition Group of similar kingdomsGroup of similar kingdoms Group of similar phylaGroup of similar phyla Group of similar classesGroup of similar classes Group of similar ordersGroup of similar orders Group of similar familiesGroup of similar families Group of similar generaGroup of similar genera Group of similar speciesGroup of similar species

1010

Classifying OrganismsClassifying Organisms

Groups Groups DDomainomain KKingdomingdom PPhylumhylum CClasslass OOrder rder FFamilyamily GGenusenus SSpeciespecies

Diverse

Similar

Biggest

Smallest

Danish Kings Play Chess On Fine Green Silk

1111

Identifying OrganismsIdentifying Organisms

Field GuidesField Guides Use:Use: ImageImage DescriptionDescription General infoGeneral info RangeRange Common nameCommon name Scientific nameScientific name

1212

Identifying OrganismsIdentifying Organisms Dichotomous KeysDichotomous Keys Use: Use:

Pairs of descriptionsPairs of descriptions OR a question that can be OR a question that can be

answered in ONLY 2 waysanswered in ONLY 2 ways

Read both descriptions or Read both descriptions or questionquestion

Choose oneChoose one Follow directions for next Follow directions for next

stepstep End up with a scientific End up with a scientific

namename

Ex: Ex: 1a.   This organism has an exoskeleton    - go to number 2 1a.   This organism has an exoskeleton    - go to number 2 1b.   This organism has an endoskeleton or no skeleton    - go to number 3 1b.   This organism has an endoskeleton or no skeleton    - go to number 3

1313

Identifying OrganismsIdentifying Organisms

SpeciesSpecies UniqueUnique Differences in Differences in

appearance and appearance and structurestructure

Ex: Paramecium Ex: Paramecium syngenssyngens Once thought to be a Once thought to be a

single speciessingle species Look similar, but other Look similar, but other

differencesdifferences

1414

SpeciesSpecies

Biological speciesBiological species Defined by 1942 – Defined by 1942 –

Ernst MayrErnst Mayr:: A group of organisms A group of organisms

that can reproduce that can reproduce only among only among themselves and are themselves and are usually contained in a usually contained in a geographic regiongeographic region

1515

HybridsHybrids

HybridsHybrids Offspring produced by Offspring produced by

different species different species interbreedinginterbreeding

Reproductive barriers Reproductive barriers not completenot complete

Some are fertile!Some are fertile! Ex: Dogs and wolvesEx: Dogs and wolves

Dogs = Dogs = Canis familiarisCanis familiaris Wolves = Wolves = Canis lupusCanis lupus

1616

Biological Species ConceptBiological Species Concept

Reproduction:Reproduction: Most of kingdom Most of kingdom

Animalia = limitedAnimalia = limited Strong barriers Strong barriers

““Species only” fails in: Species only” fails in: Organisms that Organisms that

reproduce asexuallyreproduce asexually Ex: prokaryotesEx: prokaryotes

Transfer genes Transfer genes outside of outside of reproductionreproduction

Still working on how Still working on how to classify themto classify them

1717

17.2 Classification of Species17.2 Classification of Species

Put into groups based on Put into groups based on similarities and differencessimilarities and differences More similar = closely relatedMore similar = closely related Suspect common ancestorSuspect common ancestor

1818

Classification of SpeciesClassification of Species

Similarity of structure Similarity of structure can be misleadingcan be misleading

NotNot all all characteristics characteristics inherited by offspringinherited by offspring

Ex: WingsEx: Wings Both birds and Both birds and

insects have . . .insects have . . .

1919

PhylogenyPhylogeny

Evolutionary history for a group of Evolutionary history for a group of speciesspecies

2020

Looking at Looking at StructuresStructures

Convergent evolutionConvergent evolution Converge = Come Converge = Come

togethertogether When similarities develop When similarities develop

in organisms in organisms not not closely closely related b/crelated b/c Live in similar habitats thus Live in similar habitats thus

have similar adaptationshave similar adaptations

Analogous charactersAnalogous characters Arise through convergent Arise through convergent

evolutionevolution2121

Characters in GroupsCharacters in Groups

Ancestral characterAncestral character Feature in common Feature in common

ancestor of both ancestor of both groupsgroups

Ex: Ex: BackboneBackbone

Birds and mammalsBirds and mammals

2222

Characters in GroupsCharacters in Groups

Derived characterDerived character Found in only Found in only somesome

members of a groupmembers of a group More shared = more More shared = more

closely relatedclosely related Ex: FeathersEx: Feathers

Birds but Not Birds but Not mammalsmammals

2323

CladisticsCladistics Classification based Classification based

on common ancestryon common ancestry CladeClade - group of - group of

species that shares a species that shares a common ancestorcommon ancestor

2424

CladogramCladogram CladogramCladogram

Branching diagramBranching diagram Shows hypothesized Shows hypothesized

evolutionary evolutionary relationshipsrelationships

Tips represent Tips represent groups of descendent groups of descendent taxataxa

Nodes represent Nodes represent common ancestorscommon ancestors

2525

CladisticsCladistics

OutgroupOutgroup – shares no derived – shares no derived characters with other groups being characters with other groups being studiedstudied

2626

CladogramCladogram Shared Shared derived characterderived character

Evidence that groups are closely relatedEvidence that groups are closely related Ex: mammary glandsEx: mammary glands

Shared Shared ancestral ancestral characterscharacters Not evidence groups are closely relatedNot evidence groups are closely related Ex: LimbsEx: Limbs

Classification 12 min

2727

CladogramsCladograms

StrengthsStrengths ObjectivityObjectivity Either character exists or Either character exists or

doesn’tdoesn’t

Weakness Weakness Each character treated Each character treated

the samethe same Character impact or Character impact or

importance ignoredimportance ignored

2828

Phylogenetic TreePhylogenetic Tree

Taxonomist Taxonomist assign assign importanceimportance to to characterscharacters Branching tree-like Branching tree-like

diagram diagram Shows evolutionary Shows evolutionary

relationshipsrelationships inferredinferred

2929

Molecular EvidenceMolecular Evidence

Uses DNA to show Uses DNA to show relationshipsrelationships Often considered the “last Often considered the “last

word” by scientistsword” by scientists

Usually agrees with Usually agrees with classification that was classification that was based on physical based on physical appearancesappearances Reclassification sometimes Reclassification sometimes

necessarynecessary3030

17.3 Molecular Clocks17.3 Molecular Clocks

Models that use mutation Models that use mutation rates to estimate rates to estimate evolutionary timeevolutionary time Hypothesized that changes Hypothesized that changes

in DNA “add up”in DNA “add up”

Rate of mutations = Rate of mutations = “ticking” of time“ticking” of time

More mutations = less More mutations = less closely relatedclosely related

3131

Mitochondrial DNAMitochondrial DNA

mtDNAmtDNA Found only in mitochondriaFound only in mitochondria Only Only inherited from motherinherited from mother

Sperm loses mitochondria after fertilizationSperm loses mitochondria after fertilization

Mutation rate ~10x faster than nuclear DNAMutation rate ~10x faster than nuclear DNA Often used as molecular clockOften used as molecular clock Help classify Help classify closelyclosely related organisms related organisms

3232

Ribosomal RNARibosomal RNA

rRNArRNA Useful when comparing different species Useful when comparing different species

that may be that may be veryvery distantlydistantly related related Lots of time has passedLots of time has passed

Lower mutation rateLower mutation rate Was used to reclassify Archaea and Was used to reclassify Archaea and

Bacteria into different domainsBacteria into different domains

3333

17.4 Domains and Kingdoms17.4 Domains and Kingdoms

DomainDomain Largest, broadest groupLargest, broadest group

Recent classification Recent classification groupgroup 1977, Carl Woese1977, Carl Woese

AmericanAmerican Prokaryotes differ Prokaryotes differ

fundamentally in rRNAfundamentally in rRNA

3434

3535

Domain BacteriaDomain Bacteria

Contains kingdom BacteriaContains kingdom Bacteria Unicellular prokaryotesUnicellular prokaryotes Contains autotrophs and Contains autotrophs and

heterotrophsheterotrophs Classified by:Classified by:

ShapeShape Need for oxygenNeed for oxygen Whether the cause diseaseWhether the cause disease

3636

Domain ArchaeaDomain Archaea

Contain kingdom ArchaeaContain kingdom Archaea Unicellular prokaryotesUnicellular prokaryotes Some autotrophic, some heterotrophicSome autotrophic, some heterotrophic

3737

Domain ArchaeaDomain Archaea

Cell walls do NOT contain peptidoglycanCell walls do NOT contain peptidoglycan Live in “extreme” environmentsLive in “extreme” environments

Salt lakesSalt lakes Antarctic watersAntarctic waters Deep sea ventsDeep sea vents Hot geysersHot geysers

3838

Domains Archaea and Domains Archaea and BacteriaBacteria

No true “species”No true “species” Genes are shared outside of typical Genes are shared outside of typical

reproductionreproduction Still trying to decide how to classifyStill trying to decide how to classify Used to be classified together in one Used to be classified together in one

kingdom: Monerakingdom: Monera

3939

Domain EukaryaDomain Eukarya

Includes kingdoms:Includes kingdoms: ProtistaProtista PlantaePlantae FungiFungi AnimaliaAnimalia

Eukaryotic cellsEukaryotic cells Unicellular or multicellularUnicellular or multicellular

4040

Review of KingdomsReview of Kingdoms

BacteriaBacteria ArchaeArchae ProtistaProtista FungiFungi PlantaePlantae AnimaliaAnimalia

4141

Kingdom BacteriaKingdom Bacteria

Cell wall made of Cell wall made of peptidoglycanpeptidoglycan Web-like Web-like

carbohydrate carbohydrate strands and strands and peptide bridgespeptide bridges

4242

Kingdom ArchaeaKingdom Archaea

Cell wall Cell wall No No peptidoglycanpeptidoglycan

Cell membrane Cell membrane Different lipids than Different lipids than

bacteria or bacteria or eukaryoteseukaryotes

4343

Kingdom ProtistaKingdom Protista Many unicellularMany unicellular Some have cell Some have cell

wallswalls Heterotrophs or Heterotrophs or

autotrophsautotrophs Many moveMany move Most reproduce Most reproduce

asexuallyasexually

4444

Kingdom FungiKingdom Fungi

Most multicellularMost multicellular Except yeastsExcept yeasts

Cell walls contain Cell walls contain chitinchitin Tough carbohydrateTough carbohydrate

HeterotrophicHeterotrophic

4545

Kingdom PlantaeKingdom Plantae MulticellularMulticellular Cell wallsCell walls

Cellulose (complex Cellulose (complex carb)carb)

EukaryoticEukaryotic AutotrophicAutotrophic

4646

Kingdom AnimaliaKingdom Animalia MulticellularMulticellular HeterotrophsHeterotrophs EukaryoticEukaryotic Mostly diploid cellsMostly diploid cells No cell wallNo cell wall Organized cellsOrganized cells MotilityMotility

4747

4848

4949